Method of preparing finely-divided metals



UNITED STATES PATENT OFFICE.

ALBERT MCG'ALL, OF NEW YORK, N. Y.

No Drawing. Application filed September 16, 1918, Serial No. 254,346.

Specification of Letters Patent.

Patented Nov. 15, 1921.

Renewed February 2, 1921.

Serial No. 442,012.

To all whom it may concern Be it known that I, ALBERT MoGALL, a citizenof the United States, residing at New York, in the county of New Yorkand State of New York, have invented certain new and useful Improvementsin Methods of Preparing Finely-Divided Metals, of which the following isa specification.

This invention is an electrolytic method whereby oxidizable metals, suchfor example as zinc, copper, aluminum, etc., may be prepared in a stateof minute subdivision but in non-oxidized condition. The metals soprepared are useful for a wide variety of purposes, among which may bementioned the preparation of electrodes for primary or secondarybatteries, and the manufacture of explosives of the known typecomprising a metallic component and an oxidizing agent, such for exampleas ammonium nitrate.

I will describe my invention by reference to the preparation ofnon-oxidized zinc in minutely sudivided state, as a typical orillustrative example thereof. It will be understood, however, that theinvention is not restricted to the particular manipulative details belowdescribed, since the composition and concentration of the electrolyte,as well as the current conditions, may be rather widely varied.Obviously also the conditions will be somewhat varied according to theparticular metal which it is desired to obtain in subdivided form.

I prefer to proceed as follows:

Sheet zinc, which has preferably been amalgamated (although this is notessential) is coated by rubbing or otherwise with a thln layer of asuitable oleaginous substance, such for example as an organic or inorganc (hydrocarbon) oil or grease, or material containing the same. Themineral grease known to the trade as sponge grease, and having thecharacteristics of a non-flowing grease or oil, is entirely satisfactoryfor my purposes.

The coated sheet is then connected as the anode in a suitableelectrolyte, which is preferably acid, and may consist initially of asulfuric acid solution having a specific gravity of about 1.3. Asuitable cathode is provided which is preferably also of zinc: foralthough other metallic or conductive materials may be employed ascathode, there is less liability to loss of metal by local action whenzinc is used. Also, I prefer to apply a like oleaginous coating to thecathode although this is not necessary for the practice of theinvention. The coating of the cathode is, however, a distinct advantagefor the reason that the cathode, if provided with an oleaginous coating,is not acted upon by the electrolyte when the flow of current isinterrupted.

Unidirectional current from an outside source is then caused to flowfrom the coated sheet zinc as anode, whereupon, irrespective of thecurrent density employed, a deposit of sponge or minutely subdividedzinc will be formed. This deposit is at most only loosely adherent tothe cathode, and may be either continuously or intermittently removedfrom the electrolyte, washed and dried. A current density of about oneampere per square inch of cathode surface will be found satisfactory;and the anode and cathode areas may be substantially equal.

Contrary to what might be anticipated from the known insulatingcharacter of oleaginous materials, it will be found that the coatedmetal, although quite unafiected by the acid electrolyte so long as nocurrent flows through the system, nevertheless passes freely intosolution as soon as current is applied from an external source, and issimultaneously deposited in minutely subdivided or sponge form at thecathode. Instead, however, of forming a highly oxidizable, unstable, andoften partially oxidized sponge, as is the case when the oleaginouscoating is omitted, the deposit will be found to be substantiallynon-oxidized, and relatively very stable. This I now attribute to thepresence upon the individual particles of the deposit of an oleaginousprotective coating of extreme tenuity.

Finely subdivided copper is readily prepared under the above conditions.Metallic aluminum in minute subdivision may also be prepared insubstantially the same manner. The aluminum deposit is however moreliable to oxidation than zinc when removed from the solution, andespecially when spread in contact with air. Consequently the aluminumdeposit should preferably be shielded to a reasonable degree fromoxidizing influences, as for example by storing in an inert atmosphere,or even by compressing in order to reduce the exposed surface.

Metals which have been treated with an oleaginous material and therebyrendered in active toward acid electrolytes so long as no current flowsthrough an electric circuit in which they may be included as anode, areconveniently referred to as immunized metals The immunity from purelychemi cal as distinguished from electrochemical attack thus conferred isremarkably persistent; and, particularly in the case of electrodes whichhave been in use for some time, may persist after thorough wiping of theelectrode, and even after washing it with such cleansing agents asgasolene, etc., until all apparent traces of the oleaginous coating havebeen removed. I employ the expression immunized metal anode in theclaims to designate anodes possessing the above described characteristicdue to the previous treatment with oil or equivalent material.

The term metal is used herein to include alloys, to which the method islikewise applicable.

I claim 1. Method of preparing oXidizable metals in minutely subdivided,non-oxidizedcondition, comprising electrodepositing the metal in spongeform by means of an electric current flowing from an immunized metalanode.

2. Method of preparing oXidizable metals in minutely subdivided,non-oxidized condition, comprising electrodepositing the metal in spongeform by means of an electric current flowing from an anode of the samemetal, said anode presenting surfaces having an oleaginous coating.

3. Method of preparing oxidizable metals in minutely subdivided,non-oxidized condition, comprising electrodepositing the metal in spongeform by means of an electric current passing between an anode andcathode of the desired metal, said anode immunized by treatment with anoleaginous substance.

4. Method of preparing oXidizable metals in minutely sudivided,non-oxidized condition, comprising electrodepositing the metal in spongeform by means of an electric current passing between an anode andcathode of the desired metal, both of said electrodes immunized bytreatment with an oleaginous substance.

In testimony whereof, I aflix my signature.

ALBERT MoGALL.

